[openssh.git] / cipher.c

/*
 * 
 * cipher.c
 * 
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * 
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * 
 * Created: Wed Apr 19 17:41:39 1995 ylo
 * 
 */

#include "includes.h"
RCSID("$Id$");

#include "ssh.h"
#include "cipher.h"

#ifdef HAVE_OPENSSL
#include <openssl/md5.h>
#endif
#ifdef HAVE_SSL
#include <ssl/md5.h>
#endif

/*
 * What kind of tripple DES are these 2 routines?
 *
 * Why is there a redundant initialization vector?
 *
 * If only iv3 was used, then, this would till effect have been
 * outer-cbc. However, there is also a private iv1 == iv2 which
 * perhaps makes differential analysis easier. On the other hand, the
 * private iv1 probably makes the CRC-32 attack ineffective. This is a
 * result of that there is no longer any known iv1 to use when
 * choosing the X block.
 */
void
SSH_3CBC_ENCRYPT(des_key_schedule ks1,
		 des_key_schedule ks2, des_cblock * iv2,
		 des_key_schedule ks3, des_cblock * iv3,
		 void *dest, void *src,
		 unsigned int len)
{
	des_cblock iv1;

	memcpy(&iv1, iv2, 8);

	des_cbc_encrypt(src, dest, len, ks1, &iv1, DES_ENCRYPT);
	memcpy(&iv1, (char *)dest + len - 8, 8);

	des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_DECRYPT);
	memcpy(iv2, &iv1, 8);	/* Note how iv1 == iv2 on entry and exit. */

	des_cbc_encrypt(dest, dest, len, ks3, iv3, DES_ENCRYPT);
	memcpy(iv3, (char *)dest + len - 8, 8);
}

void
SSH_3CBC_DECRYPT(des_key_schedule ks1,
		 des_key_schedule ks2, des_cblock * iv2,
		 des_key_schedule ks3, des_cblock * iv3,
		 void *dest, void *src,
		 unsigned int len)
{
	des_cblock iv1;

	memcpy(&iv1, iv2, 8);

	des_cbc_encrypt(src, dest, len, ks3, iv3, DES_DECRYPT);
	memcpy(iv3, (char *)src + len - 8, 8);

	des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_ENCRYPT);
	memcpy(iv2, (char *)dest + len - 8, 8);

	des_cbc_encrypt(dest, dest, len, ks1, &iv1, DES_DECRYPT);
	/* memcpy(&iv1, iv2, 8); */
	/* Note how iv1 == iv2 on entry and exit. */
}

/*
 * SSH uses a variation on Blowfish, all bytes must be swapped before
 * and after encryption/decryption. Thus the swap_bytes stuff (yuk).
 */
static void
swap_bytes(const unsigned char *src, unsigned char *dst_, int n)
{
	/* dst must be properly aligned. */
	u_int32_t *dst = (u_int32_t *) dst_;
	union {
		u_int32_t i;
		char c[4];
	} t;

	/* Process 8 bytes every lap. */
	for (n = n / 8; n > 0; n--) {
		t.c[3] = *src++;
		t.c[2] = *src++;
		t.c[1] = *src++;
		t.c[0] = *src++;
		*dst++ = t.i;

		t.c[3] = *src++;
		t.c[2] = *src++;
		t.c[1] = *src++;
		t.c[0] = *src++;
		*dst++ = t.i;
	}
}

void (*cipher_attack_detected) (const char *fmt,...) = fatal;

static inline void
detect_cbc_attack(const unsigned char *src,
		  unsigned int len)
{
	return;

	log("CRC-32 CBC insertion attack detected");
	cipher_attack_detected("CRC-32 CBC insertion attack detected");
}

/*
 * Names of all encryption algorithms.
 * These must match the numbers defined in cipher.h.
 */
static char *cipher_names[] =
{
	"none",
	"idea",
	"des",
	"3des",
	"tss",
	"rc4",
	"blowfish"
};

/*
 * Returns a bit mask indicating which ciphers are supported by this
 * implementation.  The bit mask has the corresponding bit set of each
 * supported cipher.
 */

unsigned int 
cipher_mask()
{
	unsigned int mask = 0;
	mask |= 1 << SSH_CIPHER_3DES;		/* Mandatory */
	mask |= 1 << SSH_CIPHER_BLOWFISH;
	return mask;
}

/* Returns the name of the cipher. */

const char *
cipher_name(int cipher)
{
	if (cipher < 0 || cipher >= sizeof(cipher_names) / sizeof(cipher_names[0]) ||
	    cipher_names[cipher] == NULL)
		fatal("cipher_name: bad cipher number: %d", cipher);
	return cipher_names[cipher];
}

/*
 * Parses the name of the cipher.  Returns the number of the corresponding
 * cipher, or -1 on error.
 */

int
cipher_number(const char *name)
{
	int i;
	for (i = 0; i < sizeof(cipher_names) / sizeof(cipher_names[0]); i++)
		if (strcmp(cipher_names[i], name) == 0 &&
		    (cipher_mask() & (1 << i)))
			return i;
	return -1;
}

/*
 * Selects the cipher, and keys if by computing the MD5 checksum of the
 * passphrase and using the resulting 16 bytes as the key.
 */

void 
cipher_set_key_string(CipherContext *context, int cipher,
		      const char *passphrase, int for_encryption)
{
	MD5_CTX md;
	unsigned char digest[16];

	MD5_Init(&md);
	MD5_Update(&md, (const unsigned char *) passphrase, strlen(passphrase));
	MD5_Final(digest, &md);

	cipher_set_key(context, cipher, digest, 16, for_encryption);

	memset(digest, 0, sizeof(digest));
	memset(&md, 0, sizeof(md));
}

/* Selects the cipher to use and sets the key. */

void 
cipher_set_key(CipherContext *context, int cipher,
	       const unsigned char *key, int keylen, int for_encryption)
{
	unsigned char padded[32];

	/* Set cipher type. */
	context->type = cipher;

	/* Get 32 bytes of key data.  Pad if necessary.  (So that code
	   below does not need to worry about key size). */
	memset(padded, 0, sizeof(padded));
	memcpy(padded, key, keylen < sizeof(padded) ? keylen : sizeof(padded));

	/* Initialize the initialization vector. */
	switch (cipher) {
	case SSH_CIPHER_NONE:
		/*
		 * Has to stay for authfile saving of private key with no
		 * passphrase
		 */
		break;

	case SSH_CIPHER_3DES:
		/*
		 * Note: the least significant bit of each byte of key is
		 * parity, and must be ignored by the implementation.  16
		 * bytes of key are used (first and last keys are the same).
		 */
		if (keylen < 16)
			error("Key length %d is insufficient for 3DES.", keylen);
		des_set_key((void *) padded, context->u.des3.key1);
		des_set_key((void *) (padded + 8), context->u.des3.key2);
		if (keylen <= 16)
			des_set_key((void *) padded, context->u.des3.key3);
		else
			des_set_key((void *) (padded + 16), context->u.des3.key3);
		memset(context->u.des3.iv2, 0, sizeof(context->u.des3.iv2));
		memset(context->u.des3.iv3, 0, sizeof(context->u.des3.iv3));
		break;

	case SSH_CIPHER_BLOWFISH:
		BF_set_key(&context->u.bf.key, keylen, padded);
		memset(context->u.bf.iv, 0, 8);
		break;

	default:
		fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher));
	}
	memset(padded, 0, sizeof(padded));
}

/* Encrypts data using the cipher. */

void 
cipher_encrypt(CipherContext *context, unsigned char *dest,
	       const unsigned char *src, unsigned int len)
{
	if ((len & 7) != 0)
		fatal("cipher_encrypt: bad plaintext length %d", len);

	switch (context->type) {
	case SSH_CIPHER_NONE:
		memcpy(dest, src, len);
		break;

	case SSH_CIPHER_3DES:
		SSH_3CBC_ENCRYPT(context->u.des3.key1,
				 context->u.des3.key2, &context->u.des3.iv2,
				 context->u.des3.key3, &context->u.des3.iv3,
				 dest, (void *) src, len);
		break;

	case SSH_CIPHER_BLOWFISH:
		swap_bytes(src, dest, len);
		BF_cbc_encrypt(dest, dest, len,
		               &context->u.bf.key, context->u.bf.iv,
			       BF_ENCRYPT);
		swap_bytes(dest, dest, len);
		break;

	default:
		fatal("cipher_encrypt: unknown cipher: %s", cipher_name(context->type));
	}
}

/* Decrypts data using the cipher. */

void 
cipher_decrypt(CipherContext *context, unsigned char *dest,
	       const unsigned char *src, unsigned int len)
{
	if ((len & 7) != 0)
		fatal("cipher_decrypt: bad ciphertext length %d", len);

	switch (context->type) {
	case SSH_CIPHER_NONE:
		memcpy(dest, src, len);
		break;

	case SSH_CIPHER_3DES:
		/* CRC-32 attack? */
		SSH_3CBC_DECRYPT(context->u.des3.key1,
				 context->u.des3.key2, &context->u.des3.iv2,
				 context->u.des3.key3, &context->u.des3.iv3,
				 dest, (void *) src, len);
		break;

	case SSH_CIPHER_BLOWFISH:
		detect_cbc_attack(src, len);
		swap_bytes(src, dest, len);
		BF_cbc_encrypt((void *) dest, dest, len,
			       &context->u.bf.key, context->u.bf.iv,
			       BF_DECRYPT);
		swap_bytes(dest, dest, len);
		break;

	default:
		fatal("cipher_decrypt: unknown cipher: %s", cipher_name(context->type));
	}
}
Commit	Line	Data
8efc0c15	1	/*
5260325f	2	*
	3	* cipher.c
	4	*
	5	* Author: Tatu Ylonen <ylo@cs.hut.fi>
	6	*
	7	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
	8	* All rights reserved
	9	*
	10	* Created: Wed Apr 19 17:41:39 1995 ylo
	11	*
	12	*/
8efc0c15	13
	14	#include "includes.h"
	15	RCSID("$Id$");
	16
	17	#include "ssh.h"
	18	#include "cipher.h"
	19
5881cd60	20	#ifdef HAVE_OPENSSL
8efc0c15	21	#include <openssl/md5.h>
5881cd60	22	#endif
	23	#ifdef HAVE_SSL
	24	#include <ssl/md5.h>
	25	#endif
8efc0c15	26
	27	/*
	28	* What kind of tripple DES are these 2 routines?
	29	*
	30	* Why is there a redundant initialization vector?
	31	*
	32	* If only iv3 was used, then, this would till effect have been
	33	* outer-cbc. However, there is also a private iv1 == iv2 which
	34	* perhaps makes differential analysis easier. On the other hand, the
	35	* private iv1 probably makes the CRC-32 attack ineffective. This is a
	36	* result of that there is no longer any known iv1 to use when
	37	* choosing the X block.
	38	*/
	39	void
	40	SSH_3CBC_ENCRYPT(des_key_schedule ks1,
5260325f	41	des_key_schedule ks2, des_cblock * iv2,
5260325f	42	des_key_schedule ks3, des_cblock * iv3,
8efc0c15	43	void dest, void src,
	44	unsigned int len)
	45	{
5260325f	46	des_cblock iv1;
8efc0c15	47
5260325f	48	memcpy(&iv1, iv2, 8);
8efc0c15	49
5260325f	50	des_cbc_encrypt(src, dest, len, ks1, &iv1, DES_ENCRYPT);
7dc6fc6d	51	memcpy(&iv1, (char *)dest + len - 8, 8);
8efc0c15	52
5260325f	53	des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_DECRYPT);
5260325f	54	memcpy(iv2, &iv1, 8); /* Note how iv1 == iv2 on entry and exit. */
8efc0c15	55
5260325f	56	des_cbc_encrypt(dest, dest, len, ks3, iv3, DES_ENCRYPT);
7dc6fc6d	57	memcpy(iv3, (char *)dest + len - 8, 8);
8efc0c15	58	}
	59
	60	void
	61	SSH_3CBC_DECRYPT(des_key_schedule ks1,
5260325f	62	des_key_schedule ks2, des_cblock * iv2,
5260325f	63	des_key_schedule ks3, des_cblock * iv3,
8efc0c15	64	void dest, void src,
	65	unsigned int len)
	66	{
5260325f	67	des_cblock iv1;
8efc0c15	68
5260325f	69	memcpy(&iv1, iv2, 8);
8efc0c15	70
5260325f	71	des_cbc_encrypt(src, dest, len, ks3, iv3, DES_DECRYPT);
7dc6fc6d	72	memcpy(iv3, (char *)src + len - 8, 8);
8efc0c15	73
5260325f	74	des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_ENCRYPT);
7dc6fc6d	75	memcpy(iv2, (char *)dest + len - 8, 8);
8efc0c15	76
5260325f	77	des_cbc_encrypt(dest, dest, len, ks1, &iv1, DES_DECRYPT);
	78	/* memcpy(&iv1, iv2, 8); */
	79	/* Note how iv1 == iv2 on entry and exit. */
8efc0c15	80	}
	81
	82	/*
	83	* SSH uses a variation on Blowfish, all bytes must be swapped before
	84	* and after encryption/decryption. Thus the swap_bytes stuff (yuk).
	85	*/
5260325f	86	static void
8efc0c15	87	swap_bytes(const unsigned char src, unsigned char dst_, int n)
8efc0c15	88	{
5260325f	89	/* dst must be properly aligned. */
	90	u_int32_t dst = (u_int32_t ) dst_;
	91	union {
	92	u_int32_t i;
	93	char c[4];
	94	} t;
	95
	96	/* Process 8 bytes every lap. */
	97	for (n = n / 8; n > 0; n--) {
	98	t.c[3] = *src++;
	99	t.c[2] = *src++;
	100	t.c[1] = *src++;
	101	t.c[0] = *src++;
	102	*dst++ = t.i;
	103
	104	t.c[3] = *src++;
	105	t.c[2] = *src++;
	106	t.c[1] = *src++;
	107	t.c[0] = *src++;
	108	*dst++ = t.i;
	109	}
8efc0c15	110	}
8efc0c15	111
5260325f	112	void (cipher_attack_detected) (const char fmt,...) = fatal;
8efc0c15	113
906a2515	114	static inline void
8efc0c15	115	detect_cbc_attack(const unsigned char *src,
	116	unsigned int len)
	117	{
5260325f	118	return;
	119
	120	log("CRC-32 CBC insertion attack detected");
	121	cipher_attack_detected("CRC-32 CBC insertion attack detected");
8efc0c15	122	}
8efc0c15	123
aa3378df	124	/*
	125	* Names of all encryption algorithms.
	126	* These must match the numbers defined in cipher.h.
	127	*/
8efc0c15	128	static char *cipher_names[] =
8efc0c15	129	{
5260325f	130	"none",
	131	"idea",
	132	"des",
	133	"3des",
	134	"tss",
	135	"rc4",
	136	"blowfish"
8efc0c15	137	};
8efc0c15	138
aa3378df	139	/*
	140	* Returns a bit mask indicating which ciphers are supported by this
	141	* implementation. The bit mask has the corresponding bit set of each
	142	* supported cipher.
	143	*/
8efc0c15	144
5260325f	145	unsigned int
5260325f	146	cipher_mask()
8efc0c15	147	{
5260325f	148	unsigned int mask = 0;
	149	mask \|= 1 << SSH_CIPHER_3DES; /* Mandatory */
	150	mask \|= 1 << SSH_CIPHER_BLOWFISH;
	151	return mask;
8efc0c15	152	}
	153
	154	/* Returns the name of the cipher. */
	155
5260325f	156	const char *
5260325f	157	cipher_name(int cipher)
8efc0c15	158	{
5260325f	159	if (cipher < 0 \|\| cipher >= sizeof(cipher_names) / sizeof(cipher_names[0]) \|\|
	160	cipher_names[cipher] == NULL)
	161	fatal("cipher_name: bad cipher number: %d", cipher);
	162	return cipher_names[cipher];
8efc0c15	163	}
8efc0c15	164
aa3378df	165	/*
	166	* Parses the name of the cipher. Returns the number of the corresponding
	167	* cipher, or -1 on error.
	168	*/
8efc0c15	169
	170	int
	171	cipher_number(const char *name)
	172	{
5260325f	173	int i;
	174	for (i = 0; i < sizeof(cipher_names) / sizeof(cipher_names[0]); i++)
	175	if (strcmp(cipher_names[i], name) == 0 &&
	176	(cipher_mask() & (1 << i)))
	177	return i;
	178	return -1;
8efc0c15	179	}
8efc0c15	180
aa3378df	181	/*
	182	* Selects the cipher, and keys if by computing the MD5 checksum of the
	183	* passphrase and using the resulting 16 bytes as the key.
	184	*/
8efc0c15	185
5260325f	186	void
	187	cipher_set_key_string(CipherContext *context, int cipher,
	188	const char *passphrase, int for_encryption)
8efc0c15	189	{
5260325f	190	MD5_CTX md;
	191	unsigned char digest[16];
	192
	193	MD5_Init(&md);
	194	MD5_Update(&md, (const unsigned char *) passphrase, strlen(passphrase));
	195	MD5_Final(digest, &md);
	196
	197	cipher_set_key(context, cipher, digest, 16, for_encryption);
	198
	199	memset(digest, 0, sizeof(digest));
	200	memset(&md, 0, sizeof(md));
8efc0c15	201	}
	202
	203	/* Selects the cipher to use and sets the key. */
	204
5260325f	205	void
	206	cipher_set_key(CipherContext *context, int cipher,
	207	const unsigned char *key, int keylen, int for_encryption)
8efc0c15	208	{
5260325f	209	unsigned char padded[32];
	210
	211	/* Set cipher type. */
	212	context->type = cipher;
	213
	214	/* Get 32 bytes of key data. Pad if necessary. (So that code
	215	below does not need to worry about key size). */
	216	memset(padded, 0, sizeof(padded));
	217	memcpy(padded, key, keylen < sizeof(padded) ? keylen : sizeof(padded));
	218
	219	/* Initialize the initialization vector. */
	220	switch (cipher) {
	221	case SSH_CIPHER_NONE:
aa3378df	222	/*
	223	* Has to stay for authfile saving of private key with no
	224	* passphrase
	225	*/
5260325f	226	break;
	227
	228	case SSH_CIPHER_3DES:
aa3378df	229	/*
	230	* Note: the least significant bit of each byte of key is
	231	* parity, and must be ignored by the implementation. 16
	232	* bytes of key are used (first and last keys are the same).
	233	*/
5260325f	234	if (keylen < 16)
	235	error("Key length %d is insufficient for 3DES.", keylen);
	236	des_set_key((void *) padded, context->u.des3.key1);
	237	des_set_key((void *) (padded + 8), context->u.des3.key2);
	238	if (keylen <= 16)
	239	des_set_key((void *) padded, context->u.des3.key3);
	240	else
	241	des_set_key((void *) (padded + 16), context->u.des3.key3);
	242	memset(context->u.des3.iv2, 0, sizeof(context->u.des3.iv2));
	243	memset(context->u.des3.iv3, 0, sizeof(context->u.des3.iv3));
	244	break;
	245
	246	case SSH_CIPHER_BLOWFISH:
	247	BF_set_key(&context->u.bf.key, keylen, padded);
	248	memset(context->u.bf.iv, 0, 8);
	249	break;
	250
	251	default:
	252	fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher));
	253	}
	254	memset(padded, 0, sizeof(padded));
8efc0c15	255	}
	256
	257	/* Encrypts data using the cipher. */
	258
5260325f	259	void
	260	cipher_encrypt(CipherContext context, unsigned char dest,
	261	const unsigned char *src, unsigned int len)
8efc0c15	262	{
5260325f	263	if ((len & 7) != 0)
	264	fatal("cipher_encrypt: bad plaintext length %d", len);
	265
	266	switch (context->type) {
	267	case SSH_CIPHER_NONE:
	268	memcpy(dest, src, len);
	269	break;
	270
	271	case SSH_CIPHER_3DES:
	272	SSH_3CBC_ENCRYPT(context->u.des3.key1,
	273	context->u.des3.key2, &context->u.des3.iv2,
	274	context->u.des3.key3, &context->u.des3.iv3,
	275	dest, (void *) src, len);
	276	break;
	277
	278	case SSH_CIPHER_BLOWFISH:
	279	swap_bytes(src, dest, len);
	280	BF_cbc_encrypt(dest, dest, len,
	281	&context->u.bf.key, context->u.bf.iv,
	282	BF_ENCRYPT);
	283	swap_bytes(dest, dest, len);
	284	break;
	285
	286	default:
	287	fatal("cipher_encrypt: unknown cipher: %s", cipher_name(context->type));
	288	}
8efc0c15	289	}
5260325f	290
8efc0c15	291	/* Decrypts data using the cipher. */
8efc0c15	292
5260325f	293	void
	294	cipher_decrypt(CipherContext context, unsigned char dest,
	295	const unsigned char *src, unsigned int len)
8efc0c15	296	{
5260325f	297	if ((len & 7) != 0)
	298	fatal("cipher_decrypt: bad ciphertext length %d", len);
	299
	300	switch (context->type) {
	301	case SSH_CIPHER_NONE:
	302	memcpy(dest, src, len);
	303	break;
	304
	305	case SSH_CIPHER_3DES:
	306	/* CRC-32 attack? */
	307	SSH_3CBC_DECRYPT(context->u.des3.key1,
	308	context->u.des3.key2, &context->u.des3.iv2,
	309	context->u.des3.key3, &context->u.des3.iv3,
	310	dest, (void *) src, len);
	311	break;
	312
	313	case SSH_CIPHER_BLOWFISH:
	314	detect_cbc_attack(src, len);
	315	swap_bytes(src, dest, len);
	316	BF_cbc_encrypt((void *) dest, dest, len,
	317	&context->u.bf.key, context->u.bf.iv,
	318	BF_DECRYPT);
	319	swap_bytes(dest, dest, len);
	320	break;
	321
	322	default:
	323	fatal("cipher_decrypt: unknown cipher: %s", cipher_name(context->type));
	324	}
8efc0c15	325	}